A Wavelength-Division-Multiplexing (WDM) cross-connect (a non-wavelength-changing one) is a device that can exchange any wavelength channel in any line with the same wavelength channel in any other line. The conventional design is to use a matrix of switches between sets of wavelength multiplexers, such as Waveguide Grating Routers (WGRs). For example see the publications
[1] M. K. Smit, "New focusing and dispersive planar component based on an optical phased array," Electron. Lett., vol. 24, pp. 385-386 (1988); PA1 [2] H. Takahashi, S. Suzuki, K. Kato and I. Nishi, "Arrayed-waveguide grating for wavelength division multi/demultiplexer with nanometer resolution," Electron. Lett., vol. 26, pp. 87-88 (1990); and PA1 [3] C. Dragone, "An N.times.N optical multiplexer using a planar arrangement of two star couplers," IEEE Photon. Technol. Lett., vol. 3, 812-814 (1991).
For 2 line.times.2 line versions, designs have been demonstrated with discrete components {e.g., see B. Glance, "Tunable add drop optical filter providing arbitrary channel arrangements," IEEE Photon. Technol. Lett., vol. 7, 1303-1305 (1995)} and with fully integrated components {e.g., see K. Okamoto, M. Okuno, A. Himeno, and Y. Ohmori, "16-channel optical add/drop multiplexer consisting of arrayed-waveguide gratings and double-gate switches," Electron. Lett., vol. 32, 1471-1472 (1996)}.
Notwithstanding these advances in the design of WDMs, there is a continuing need to integrate the switch and WGR functions and to further reduce the size of WDMs.